A biphenyltetracarboxylic acid tetraester can be converted to a biphenyltetracarboxylic acid dianhydride which is favorably employed to prepare heat-resistant aromatic polyimide. The biphenyltetracarboxylic acid tetraester can be generally classified into 3,3′,4,4′-biphenyltetracarboxylic acid tetraester (i.e., s-BPTT) and 2,3,3′,4′-biphenyltetracarboxylic acid tetraester (i.e., a-BPTT). The s-BPTT is favorably employable for preparing highly heat-resistant polyimide, while the a-BPTT is favorably employable for preparing thermoplastic polyimide.
Japanese Patent Provisional Publication 55-141417 describes a process for preparing a biphenyltetracarboxylic acid tetraester from phthalic diester in the presence of molecular oxygen and a catalyst comprising an organic palladium compound and a copper compound. The resulting biphenyltetracarboxylic acid tetraester mainly comprises s-BPTT (3,3′,4,4′-biphenyltetracarboxylic acid tetraester).
Japanese Patent Provisional Publication 61-106541 describes a process for preparing a biphenyltetracarboxylic acid tetraester mainly comprising a-BPTT (i.e., 2,3,3′,4′-biphenyltetracarboxylic acid tetraester) from phthalic diester in the presence of molecular oxygen and a catalyst comprising an organic palladium compound and a copper compound and under such condition that a β-diketone is continuously or intermittently supplied into the reaction mixture.
Japanese Patent Provisional Publication 2003-113143 describes a process for preparing a biphenyltetracarboxylic acid tetraester mainly comprising a-BPTT from phthalic diester in the presence of molecular oxygen and a catalyst comprising a palladium complex compound having a ligand molecule containing nitrogen and oxygen.
Japanese Patent Provisional Publication 2000-302700 describes an oxidative-coupling reaction between olefin and an aromatic compound in the presence of rhodium acetylacetonato catalyst and a copper(II) redox reagent.